From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugs-return-398289-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org>
Received: (qmail 24433 invoked by alias); 10 Aug 2012 08:37:55 -0000
Received: (qmail 24422 invoked by uid 22791); 10 Aug 2012 08:37:54 -0000
X-SWARE-Spam-Status: No, hits=-3.6 required=5.0	tests=ALL_TRUSTED,AWL,BAYES_00
X-Spam-Check-By: sourceware.org
Received: from localhost (HELO gcc.gnu.org) (127.0.0.1)    by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Fri, 10 Aug 2012 08:37:33 +0000
From: "senthil_kumar.selvaraj at atmel dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/54218] New: Debug info for function parameters is incorrect when compiled with -O0
Date: Fri, 10 Aug 2012 08:37:00 -0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: new
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: middle-end
X-Bugzilla-Keywords:
X-Bugzilla-Severity: normal
X-Bugzilla-Who: senthil_kumar.selvaraj at atmel dot com
X-Bugzilla-Status: UNCONFIRMED
X-Bugzilla-Priority: P3
X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org
X-Bugzilla-Target-Milestone: ---
X-Bugzilla-Changed-Fields:
Message-ID: <bug-54218-4@http.gcc.gnu.org/bugzilla/>
X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/
Auto-Submitted: auto-generated
Content-Type: text/plain; charset="UTF-8"
MIME-Version: 1.0
Mailing-List: contact gcc-bugs-help@gcc.gnu.org; run by ezmlm
Precedence: bulk
List-Id: <gcc-bugs.gcc.gnu.org>
List-Archive: <http://gcc.gnu.org/ml/gcc-bugs/>
List-Post: <mailto:gcc-bugs@gcc.gnu.org>
List-Help: <mailto:gcc-bugs-help@gcc.gnu.org>
Sender: gcc-bugs-owner@gcc.gnu.org
X-SW-Source: 2012-08/txt/msg00561.txt.bz2

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54218

             Bug #: 54218
           Summary: Debug info for function parameters is incorrect when
                    compiled with -O0
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: senthil_kumar.selvaraj@atmel.com


Created attachment 27980
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=27980
Failing dejagnu test case

When compiling a function, like below, with no optimizations (-O0), on a x86_64
target (also occurs for atleast one other target (avr))

void func(int p)
{
    p = 0; 
    p = 32;
}

wrong debug information is emitted for the function parameter (p), that cause
the debugger to keep showing the value of the actual argument, even after p is
overwritten. A failing dejagnu test is attached.

Based on a preliminary analysis, the actual problem seems to be that stack
space for a function parameter (that is not used??) is allocated twice when
gimple_expand_cfg runs - once when expand_used_vars runs, and later when
assign_parm_setup_stack runs. expand_used_vars allocates stack space despite
the check for a default definition being present in the partition, because the
function parameter node (which I guess should be the default definition) is not
present when iterating over num_ssa_names.